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What model of Walbro carb is on a ROS 125


Capotec2015
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Hi,

Part of my troubleshooting to find out whats causing black oil leak where the ball socket joint joins the expansion chamber (not right at the barrel -thats completely dry)  and getting on the on the prop-here's what I have done so far:

Taken exhaust off and did a caustic soda bath for expansion chamber to clean out carbon and same for the joint that connects to the barrel. Re-assembled -new petrol mix at 125ml oil for 5Litres petrol -new spark plug. I have plenty of compression -so I am thinking it cant be the ring surely I would lose compression if it was the ring?

I havent done anything with the carb -only check that the high/low screws were one turn out -which they appeared to be. Rather than buy the kit, I was thinking about getting a new carb -at least I can then rule that whole unit out... 

 

Does anyone know what model the carb would be?

 

Also - is it possible that perhaps at some point a 2 ringed piston was installed and the oil ring is worn - or would that also manifest itself in less compression as well -or is that just unlikely. The original in the ROS catalogue show a single ring...

 

Apologies for all the questions but I am on a learning curve with this!

 

Thanks

 

Paul

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You will need to check needle height and pop off pressure if you going to rebuild the carb. Also I used to get a bit of leakage around my moster exhaust I got a little valve grinding paste and bedded the to halfs washing it after of coarse but for that cured it. 

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Hi Neilzy,

 

Where the oil is leaking from isnt at the flat face where it joins the barrel -that joint is dry -its a joint which appears to be almost a ball and socket type thing a couple of centimeters from the barrel with retaining springs -no gasket -check the photos -would be interested in your opinion. Like I mentioned I made up a new mixture, new plug, cleaned the exhaust out using caustic soda bath -put it all back together and still getting black oil from the same place, dripping and going on to the prop. I am just going through a process of elimination -targeting the carb next...not sure whats causing it to be honest..

 

https://www.dropbox.com/s/sfn6ow8venorjf5/IMG_0580.JPG?dl=0

https://www.dropbox.com/s/v1yvpvjnsm6ga7y/IMG_0581.JPG?dl=0

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Yeah it's a different joint to the Moster most engines will let a little past this type of exhaust joint although yours does look excessive Its been ages since I last worked on a Ros not sure if there should be some sort of "O" ring type of seal there. Not sure what to suggest I will have. Chat with my 2stroke guru see what he says

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  • 1 month later...

Hi Neilzy,

 

Just for info, I have the exploded view of the entire engine and there is no O ring or gasket shown in the diagram at that point. On further investigation, it seems the socket part of the ball/socket joint may simply be worn and what should be going past that joint is, in part, coming out of it. Ultimately a new exhaust is required, which I am happy to buy but the response from the guy at ros motor in Italy is painfully slow and sometimes they just dont respond at all. As a stop gap, I'm using a metal weld epoxy for high temp use but havent yet started the engine to see how its holding up -might get a chance tomorrow...

I recently needed to replace the compression valve and asked them to send me one - -nothing in response. The cost was something like 9 Euros plus postage. I ended up getting one from a new  Cors Air engine but it was £40!!  Oh well, at least it was an exact fit....

 

 

Edited by Capotec2015
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It's good you got to the root of the problem as I said with the ball & socket type I got some valve grinding paste and worked away till it was a snug for but I'm thinking if yours is worn and has a ridge etc that may not be posssible and as you have said a new one in order. From memory I'm thinking that the PAP dealer can't think of his name hopefully someone will come along and remind us might be able to help you I think they based in Kent in the past I've got Ross parts from them. 

Neilzy

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hey mate got the same set up 

the issue is simply the wear between the pipe and the header = not sure how to fix it but it is just a stretching? of the metal on the pipe side (mine rattles). the only thing you can do it to try to press the outer to fit the inner- metal to metal contact it is what it is on this thing (pain in the arse) if it leaks oil etc that is just gas blowing by in the non airtight join - dumb design

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  • 1 month later...

have the same issue with the exhaust- it is made to move in its socket as the lower end of the pipe has two isolation mounts (rubber) so it needs to move at both ends. a bit of oil leak is not going to stuff anything up. dont waste your money on a new pipe. we just welded mine up at the ball joint and made the isolation mounts solid so now the pipel actually vibrates iwth the engine which to me actually makes sense as now there will be no independent vibration of donk and pipe. a bit of oil is not a problem it is a two stroke. piston is only a single ring item by design. dont be tempted to much with oil % as you will seize it.

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